This invention relates to an arrangement for disassembling sealing and bearing means from rotary pipe joints, and particularly for simplifying removal of such means from rotary joints employed in fluid transfer apparatus used for conducting liquids, gases or particulate solids between transport and storage containers.
This invention is especially advantageous when embodied in marine loading arms commonly utilized for transferring crude oil and/or petroleum products between a tanker or other marine transport vessel and a terminal pipeline on a wharf or other stationary facility. As diagrammatically illustrated in FIG. 1 of the drawings, such an arm generally comprises an inner arm section 10 and an outer arm section 12 interconnected by a rotary pipe joint 14 such as that illustrated in FIG. 2, and an upstanding base or riser R upon which the inner pipe section 10 is pivotally mounted by vertical and horizontal rotary pipe joints 16, 18 that are interconnected by a pipe elbow 20. A bracket 22, secured to an element on each joint 16, 18, supports the arm so that the elbow 20 can be removed to replace or service the joint packings or seals without dismounting the arm from the riser. The outer end of the outer arm section 12 usually is provided with a triple joint assembly 24 comprising three rotary pipe joints 26, 38, 30 oriented on mutually perpendicular axes and interconnected by 90 degree pipe elbows 32, 34, and terminates in a pipe coupler 36 for releasably connecting the arm to the pipe manifold of a marine tanker (not shown). A pantograph-like sheave and cable assembly, generally comprising an inner sheave 38 rotatably mounted on the inner end of the inner arm section 10, an outer sheave 40 rotatably mounted on the outer end of the inner arm section 10 and non-rotatably secured to the outer arm section 12 as by a strut 42, and a cable 44 trained around both sheaves, provides a means to pivot the outer arm section 12 about the axis of the joint 14, and thus with respect to the inner arm section 10, when the inner sheave 38 is rotated as by hydraulic cyclinders or other suitable power means (not shown).
A conventional rotary pipe joint designed to be removable for servicing or replacement from the pipe system in which it is installed, such as the joint illustrated in FIG. 2, has several disadvantages: significant increased bulk resulting from the use of two flanges; the presence of a static seal S in addition to the conventional dynamic seal D, thereby introducing another path for potential leaks and establishing an interdependency between the bearing and static seal functions; and in order to adequately absorb significant loads either the parts of the joint must be extra heavy or the diameter of the flow passage must be increased over that of the pipes between which the joint is located.